Pallets are customarily used to transport and store goods. A pallet typically includes an upper deck and a lower deck separated by support blocks. Pallets have traditionally been formed of wood. While advantageous in terms of cost, wood pallets have many disadvantages. For example, they are subject to breakage and are therefore reusable only over a short period of time. Wooden pallets are also difficult to maintain in a sanitary condition, thereby limiting their usability in applications where sanitation is important, such as in food handling applications.
With the growth of the plastics industry a wide variety of plastics have been investigated to determine their suitability for use in producing pallets. Plastic pallets can easily be molded and are stronger and lighter weight than wooden pallets. They can also be made with recyclable materials. Furthermore, plastic pallets are more durable than wooden pallets.
In terms of durability, plastic pallets come into repeated contact with the sharp metal tines of a forklift, which is also referred to as a pallet jack. The support blocks separating the upper and lower decks are subjected to the most intense wear of any part on the pallet. In addition, if the tines of a pallet jack are inserted too far between the upper and lower decks such that the wheels of the pallet jack are resting on the lower deck, then the upper deck becomes separated from the lower deck when the tines of the pallet jack are lifted. The resulting damage from the upper deck being separated from the lower deck requires the upper deck to be replaced, and if the damage is too extensive, then the entire pallet is replaced.
If only the support blocks are damaged by the pallet jack, then they may be replaced at a cost far less than replacing the entire pallet. For example, U.S. Pat. No. 5,413,052 discloses a plastic pallet having an upper deck and a lower deck, with replaceable support blocks therebetween. The support blocks include octagonal posts having support member walls positioned beneath reinforced portions of the upper deck. The posts also have a sleeve with a central bolt hole parallel to the support member walls. The lower deck receives the support blocks in recessed pockets. Plastic bolts are inserted through the upper deck, each post, and the lower deck. Plastic T-nuts are used for holding the bolts in place.
In U.S. Pat. No. 4,843,976 a plastic pallet includes identical upper and lower decks interconnected by support blocks. Each support block includes a central core and a surrounding sleeve interconnected by spokes. The core has flexible tabs that extend beyond opposite ends of the sleeve and lock onto the base and cargo layers. The plastic pallet disclosed in U.S. Pat. No. 5,791,261 also discloses the use of flexible tabs for holding the base and cargo layers together. In particular, the plastic pallet comprises support blocks between the upper and lower decks, and upper and lower snap-lock elements extend from the respective upper and lower decks through the support blocks for inter-locking with one another.
While plastic pallets offer several advantages over wood pallets, there is still a demand to increase durability and strength of plastic pallets.